Values for `@Sequence`-annotated property generated on update

[lbueker]

Version: spring-data-jdbc:3.5.0-M1
Currently when using the @Sequence annotation in an entity, it seems to generate a new value on each save.

This results in an error, when trying to update an entity complaining that the newly generated id is not available in the database.

I think there should be a check, so it only generates a new value, when there is none set.

[mipo256]

Hey @schauder @mp911de. This problem is related to the following change: #1955
Please, assign this issue to me, I'll take a look what went wrong

[mp911de]

Thanks @lbueker for trying out milestones. @mipo256 assigned to you.